The multidrug-resistance (MDR) gene product, P-glycoprotein (Pl7O) expressed in tumor cells, has also been localized in the apical regions of secretory epithelial cells of the pregnant mouse endometrium. It has also been shown that progesterone interacts with P170 in gravid mouse endometrium. We will study the expression and localization of P170 in the human endometrium of normal controls and patients undergoing therapeutic D&C to investigate if the expression of P170 correlates with progesterone levels of the luteal phase and pregnancy and if P170 plays a role in sustaining progesterone levels necessary to maintain pregnancy.